I am thinking about installing a second sump pump in my basement. I have one corner that is constantly wet because the septic pipe runs through the wall above it and I haven't been able to get it sealed. (I've tried epoxy and hydraulic cement, but eventually it leaks again) Plus, having a second pit would just make me feel better. My main pit failed once and the basement flooded. I have since added a battery backup pump, but a second electric pump would make me feel better. My slab is about 4 inches think with 2 inches of foam below. Has anyone cut all the way through with a 7 1/2" circular saw? Do I just cut a deep as possible, then hammer out the rest?
Cutting Concrete with Circular Saw
- Thread starter Skooterj
- Start date
Walkers
Well-known member
Just cut as much as you can and hammer the rest. You might consider calling a concrete cutting company. You might end up with a better cut that needs no refinishing.
Gonna put a round pit in a square hole, it will need some refinishing no matter what
TractorJeff
Well-known member
My Dad bought a cheap Circular Saw to cut Thick Shale pieces for a side walk. The dust ate the brushes. My Brother and I cut a bunch of the floor for his basement bathroom if I remember right with a Circular Saw? I think we used water to keep the Dust down because it was an "In-House" project? That Saw sounded pretty sick afterwards if I remember correctly?
billconner
Well-known member
Maybe rent a concrete chain saw? your floor hole is going to be much (6"+) than pit to allow removing material and installing pit. Then backfill around and patch around flush with floor.
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I thought about renting a saw, but you have to buy the blade. Seems silly to buy a $60 blade plus the saw rental fee for 6 feet worth of cuts. My circular saw is on its last legs (I cut through the cord) anyway, and a 7 1/2" blade is only $15. The concrete is only 4 years old. If I destroy my saw, oh well. I will have my son holding the shop vac right next to the cut and sucking up as much dust as possible. I may wet it down a bit too.
billconner
Well-known member
Makes sense. It is tough on saws - dust and scratches in the table - but your prepared for that.
duneslider
Well-known member
I have done this quite a few times with my mag77 and a diamond blade. I even have a pump sprayer that I use to keep the cut wet while cutting. It makes a huge difference on the amount of dust and I wouldn't do it without water inside for sure. Make sure you plug into a gfci...
I did have to replace the brushes once after doing a cut without water. I haven't had any issues doing the water thing. I keep the mag 77 around for this purpose. I use a makita 36v saw for all my wood cutting now.
Just so you know, you are only going to get a cut about 2.25" deep. It will at least give you reasonably straight cuts on top but it won't get anywhere near all the way through a 4" slab. I usually do the cut the best I can then drill a bunch of holes with a rotary hammer drill and then smash it all out with a big sledge hammer and clean it up with my chipping hammer. If I did this a lot I would get a good concrete saw but doing it this way every few years is just fine for me. I have even cut control joints in concrete patios the day after a pour with this method. Works fine.
I did have to replace the brushes once after doing a cut without water. I haven't had any issues doing the water thing. I keep the mag 77 around for this purpose. I use a makita 36v saw for all my wood cutting now.
Just so you know, you are only going to get a cut about 2.25" deep. It will at least give you reasonably straight cuts on top but it won't get anywhere near all the way through a 4" slab. I usually do the cut the best I can then drill a bunch of holes with a rotary hammer drill and then smash it all out with a big sledge hammer and clean it up with my chipping hammer. If I did this a lot I would get a good concrete saw but doing it this way every few years is just fine for me. I have even cut control joints in concrete patios the day after a pour with this method. Works fine.
engineer2
Well-known member
When I did my basement we had to cut the floor for the new toilet to the ejector pump. I had a 14" abrasive cutoff saw. Took it off the base and used it to saw cut the floor. Probably not the safest way to do it, but it wasn't hard to control and it worked surprisingly well. Next time I would use a spray bottle to keep the dust down.
You can buy a 120V/15amp concrete saw or rent one from HD.
You can buy a 120V/15amp concrete saw or rent one from HD.
Walkers
Well-known member
might consider having it cored instead.
larry4406
Well-known member
Yes - cheap circle saw and concrete blade. Pump sprayer to control dust.
Cut slab as deep as it will go. Then use jack hammer to bust out between the saw cuts.
Do your deed then patch the vapor barrier, drill dowels into slab edges and wire tie, then concrete patch.
Cut slab as deep as it will go. Then use jack hammer to bust out between the saw cuts.
Do your deed then patch the vapor barrier, drill dowels into slab edges and wire tie, then concrete patch.
Half-fast eddie
Well-known member
My bet is that … 10 seconds after starting the cut … you won’t be able to see your son. And the dust cloud will hang in the air for 30 min, as it slowly settles onto everything in sight. And places you can’t imagine.
Not if I use an drywall bag in the shop vac. Those bags trap the finest dust you can imagine.
Forgottonia
Well-known member
Do you have a hammer drill? You could use masonry bits to drill holes close together in a round pattern. Then use a small sledge to knock out the hole, and chisel to clean up the sides.
kelpaso1
MEMBER EMERITUS
No an ordinary shop vac doesn't have the CFM to remove the dust your putting out.
duneslider
Well-known member
I personally have had better luck using water than a vac for this. There is still cleanup of the slurry at the end but it tends to be less invasive than the concrete dust.
I have cut a little concrete with a 7-1/4" circular saw. I had my wife spraying water from a pump up sprayer. Dust was not an issue. We replaced a basement shower stall and had to move the drain. I cut maybe a 18" square in the floor.
It kind of messed with my mind using a 120 volt saw and water, but I was plugged into a ground fault outlet.
It kind of messed with my mind using a 120 volt saw and water, but I was plugged into a ground fault outlet.
I would just use an electric breaker . you're going to need to repair the concrete anyway.
less dust,the end result looks the same .
less dust,the end result looks the same .
nadogail
Well-known member
My Buddy borrowed an electric saw from someone who owed him a favor and he made the cut with the borrowed saw; a buddy is a good thing to have.
rustyjames
Well-known member
Why even cut? I just break out the amount of concrete needed and patch.
Evilunclegrimace
Well-known member
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Recommend goggles, respirator and PPE before making all the dust you want.
how much do you enjoy swinging the sledghammer to break it up after you get halfway through?
you can get a 12" or 14" diamond blade off Amazon for $25-30. Renting a saw to put it on is ~$50/4hrs from Home Depot. You'll be done in 20 minutes instead of hours. And you can EASILY make a couple cross cuts to make the slab smaller for removal.
I'm a cheap stubborn guy often. My eyes are slowly opening to using the right tool for the job. The Circ saw will make a groove NO problem, but you're still going to have to break up that slab while the lower 2" of it is solidly attached and resting on dirt. I'd personally spend <$100 for the easier life.
you can get a 12" or 14" diamond blade off Amazon for $25-30. Renting a saw to put it on is ~$50/4hrs from Home Depot. You'll be done in 20 minutes instead of hours. And you can EASILY make a couple cross cuts to make the slab smaller for removal.
I'm a cheap stubborn guy often. My eyes are slowly opening to using the right tool for the job. The Circ saw will make a groove NO problem, but you're still going to have to break up that slab while the lower 2" of it is solidly attached and resting on dirt. I'd personally spend <$100 for the easier life.
LegacyIndustrial
ALLIANCE MEMBER
Bingo
Home Depot near me doesn't rent tools
Sunbelt does, but no 4 hour rentals. I have my 27 year old son to swing the hammer.Matt018888
Well-known member
We just mark the round hole with caulk, using a hammer drill, drill 1/2 holes fallowing the line no further than a 1" apart. Smack it with a sledge, clean it up with a chisel and presto... A pretty clean hole with a lot less dust than the options above.
that stinks. I'd go the circ saw or drill approach thenHome Depot near me doesn't rent tools
cycle61
Well-known member
I'd get a concrete coring company to come drill a 6" or whatever size hole. They'll be done in an hour and it'll be clean.
theoldwizard1
Well-known member
You probably won't make it all the way through do you will have to finish with a chisel.
Also know that you will generate massive amounts of dust that will get all of the house (and extra person with a shop vac helps). Your saw will probably be ruined.
rd65
Well-known member
If you do, use LOTS of water. You ever price a replacement chain and bar for one of those. CRAZY expensive.
If you can rent the proper tool then I would do that. The money spent will probably be well worth it in the end. I had to drill a 4" hole through 11" of concrete foundation to install a dryer vent. I tried drilling with a hammer bit around the hole and chipping it out to no avail. Wasted an entire afternoon and $20 in bits. Went to the local rental place and rented a core drill and bit for $80 and the hole was done in 12 minutes. For some reason I recorded it that day and here is a video. Made super short order of that job!